View source for Upsilon

{{short description|Twentieth letter in the Greek alphabet}}
{{hatnote group|
{{about-distinguish|the Greek upsilon|Epsilon|ʊ|Y}}
{{other uses|Upsilon (disambiguation)|Ypsilon (disambiguation)}}
}}
{{pp-pc}}
{{Greek Alphabet|letter=upsilon}}

'''Upsilon''' ({{IPAc-en|US|ˈ|ʌ|p|s|ɪ|ˌ|l|ɒ|n|,_|ˈ|(|j|)|uː|p|-|,_|-|l|ən}}, {{IPAc-en|UK|(|j|)|uː|p|ˈ|s|aɪ|l|ən|,_|ʊ|p|-|,_|-|l|ɒ|n|audio=LL-Q1860 (eng)-Flame, not lame-Upsilon.wav}};<ref name=Chambers>{{cite encyclopedia |title=upsilon |encyclopedia=[[Chambers Dictionary]] |publisher=[[Chambers (publisher)|Chambers]] |year=2003 |edition=9th |isbn=0-550-10105-5}}</ref><ref name=Collins>{{cite encyclopedia |title=upsilon |encyclopedia=[[Collins English Dictionary]] |publisher=[[HarperCollins]] |year=2018 |edition=13th |isbn=978-0-008-28437-4}}</ref>{{refn|{{cite Merriam-Webster|access-date=2016-01-22|Upsilon}}}}{{refn|{{Cite dictionary |url=http://www.lexico.com/definition/Upsilon |archive-url=https://web.archive.org/web/20191221151730/https://www.lexico.com/definition/upsilon |url-status=dead |archive-date=2019-12-21 |title=Upsilon |dictionary=[[Lexico]] UK English Dictionary |publisher=[[Oxford University Press]]}} }}{{refn|{{cite Dictionary.com|access-date=2016-01-22|upsilon}}}}<ref>{{cite OED|upsilon}}</ref> uppercase '''Υ''', lowercase '''υ'''; {{langx|el|{{linktext|ύψιλον}}}} ''ýpsilon'' {{IPA|el|ˈipsilon|}}) or '''ypsilon''' {{IPAc-en|I|p|-}}<ref name="Chambers" /> is the twentieth letter of the [[Greek alphabet]].  In the system of [[Greek numerals]], {{langx|grc|Υʹ|label=none}} has a value of 400. It is derived from the [[phoenician alphabet|Phoenician]] [[Waw (letter)|waw]] [[Image:Phoenician waw.svg|20px]].

[[File:NAMA Alphabet grec.jpg|thumb|The Greek alphabet on a [[black figure]] vessel, with a V-shaped upsilon]]

==Etymology==
The name of the letter was originally just {{lang|grc|υ}} ({{lang|grc-Latn|y}}, also called {{lang|grc|ὑ}} {{lang|grc-Latn|hy}}, hence ''[[hyoid bone|hyoid]]'', meaning 'shaped like the letter {{lang|grc|υ}}'), but the name changed to {{lang|grc|υ ψιλόν}} (={{lang|grc|υ}} {{lang|grc-Latn|psilon}}, 'u-plain' or 'u-simple') to distinguish it from {{lang|grc|οι}}, which had come to have the same {{IPA|[y]}} pronunciation.<ref>[[W. Sidney Allen]], ''Vox Graeca'', 3rd ed., Cambridge 1987, p. 69.</ref>

==Pronunciation==
In early [[Attic Greek]] (6th century BCE), it was pronounced {{IPAblink|u|}} (a [[close back rounded vowel]] like the English "long o͞o").<ref>{{Cite book|url=https://books.google.com/books?id=rXYDQwehOVMC&q=upsilon+%22back+vowel%22|title=Greek Writing from Knossos to Homer: A Linguistic Interpretation of the Origin of the Greek Alphabet and the Continuity of Ancient Greek Literacy|first=Roger D.|last=Woodard|date=June 12, 1997|publisher=Oxford University Press|isbn=9780195355666|via=Google Books}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=qmHsrNYoe4MC&q=upsilon+%22Close+back+rounded+vowel%22+greek&pg=PA12|title=Introduction to Attic Greek|first=Donald J.|last=Mastronarde|date=February 21, 2013|publisher=University of California Press|isbn=9780520275713|via=Google Books}}</ref> In [[Ancient Greek language|Classical Greek]], it was pronounced {{IPAblink|y|}} (a [[close front rounded vowel]]), at least until 1030.<ref>F. Lauritzen, "Michael the Grammarian's irony about Hypsilon. A step towards reconstructing Byzantine pronunciation", ''Byzantinoslavica'', '''67''' (2009)</ref> In [[Modern Greek]], it is pronounced {{IPA|{{IPAblink|i|}}}}; in the [[digraph (orthography)|digraph]]s {{IPA|⟨αυ⟩}} and {{IPA|⟨ευ⟩}}, as {{IPA|/f/}} or {{IPA|/v/}}; and in the digraph {{IPA|⟨ου⟩}} as {{IPA|/u/}}. In ancient Greek, it occurred in both [[Ancient Greek phonology#Vowels|long and short]] versions, but Modern Greek does not have a length distinction.

As an initial letter in Classical Greek, it always carried the [[rough breathing]] (equivalent to ''h'') as reflected in the many [[English words of Greek origin|Greek-derived English words]], such as those that begin with ''hyper-'' and ''hypo-''. This rough breathing was derived from an older pronunciation that used a [[Sibilant consonant|sibilant]] instead; this sibilant was not lost in Latin, giving rise to such cognates as ''super-'' (for ''hyper-'') and ''sub-'' (for ''hypo-'').

Upsilon participated as the second element in [[falling diphthong]]s, which have subsequently developed in various ways.

==Correspondence with Latin Y==
[[File:Y-like European letters.svg|thumb|[[U (Cyrillic)|Cyrillic '''У''']], [[Y|Latin '''Y''']] and Greek '''Υ''' (upsilon) and '''ϒ''' (hooked upsilon) in [[w:GNU FreeFont|FreeSerif]] – one of the few typefaces that distinguish between the Latin and the Greek form.]]

The use of [[Y]] in Latin dates back to the first century BC. It was used to transcribe loanwords from Greek, so it was not a native sound of Latin and was usually pronounced {{IPA|/u/}} or {{IPA|/i/}}. The latter pronunciation was the most common in the Classical period and was used mostly by uneducated people. The [[Roman Emperor]] [[Claudius]] proposed introducing a [[Claudian letters|new letter]] into the [[Latin alphabet]] to transcribe the so-called {{lang|la|sonus medius}} (a short vowel before labial consonants), but in inscriptions, the new letter was sometimes used for Greek upsilon instead.

Four letters of the [[Latin alphabet]] arose from it: [[U]], [[Y]] and, much later, [[V]] and [[W]]. In the [[Cyrillic script]], the letters [[U (Cyrillic)|U]] (У, у) and {{lang|ru-Latn|[[izhitsa]]}} (Ѵ, ѵ) arose from it.

In some languages, including [[German language|German]] and [[Portuguese language|Portuguese]], the name ''upsilon'' ({{lang|de|Ypsilon}} in German, {{lang|pt|ípsilon}} in Portuguese) is used to refer to the Latin letter '''Y''' as well as the Greek letter.  In some other languages, the (Latin) Y is referred to as a "Greek I" ({{lang|es|i griega}} in [[Spanish language|Spanish]], {{lang|fr|i grec}} in [[French language|French]]), also noting its Greek origin.

== Usage ==
* In [[particle physics]] the capital Greek letter ϒ denotes an [[Upsilon particle]]. Note that the symbol should always look like <math>\,\Upsilon</math> in order to avoid confusion with a Latin Y denoting the [[hypercharge]]. This may be done either with a font such as FreeSerif or with the dedicated Unicode character U+03D2 ϒ.
* Automobile manufacturer [[Lancia]] has a model called the [[Lancia Ypsilon|Ypsilon]].
* In the [[International Phonetic Alphabet]], the symbol {{angbr IPA|ʋ}} is used to represent a [[labiodental approximant]].
* In [[astrophysics]] and [[physical cosmology]], ϒ refers to the [[mass-to-light ratio]].<ref>Mihalas and McRae (1968), ''Galactic Astronomy'' (W. H. Freeman)</ref>
* In [[statistics]], it is sometimes used instead of v or nu to indicate [[degrees of freedom (statistics)|degrees of freedom]].<ref>{{cite book|title=Probability and Statistics for Scientists and Engineers|edition=9th|year=2017|last = Walpole|first=Ronald}}</ref>
* In the [[Persian language|Persian]] language, “one upsilon” is used to describe a positive amount close to 0 (zero).{{cn|date=November 2024}}

===Similar appearance===
* A similar symbol {{unichar|2648}} is used for the [[astrological sign]] of [[Aries (astrology)|Aries]].

==Symbolism==
[[File:Geoffrey Tory Ypsilon.jpg|thumb|[[Geoffroy Tory]] Ypsilon]]
Upsilon is known as Pythagoras' letter, or the Samian letter, because [[Pythagoras]] used it as an emblem of the path of virtue or vice.<ref>Brewer, Ebenezer Cobham. ''The reader's handbook of famous names in fiction, allusions, references, proverbs, plots, stories, and poems'', [https://books.google.com/books?id=n3kjAQAAIAAJ&pg=PA956&q=%22samian%20letter%22 Vol. 2, p. 956]. Lippincott, 1899.</ref> As the Roman writer [[Persius]] wrote in ''Satire III'':
{{quote|and the letter which spreads out into Pythagorean branches has pointed out to you the steep path which rises on the right.<ref>{{cite book|author=Persius|title=Satires|year=1920|url=https://archive.org/stream/juvenalpersiuswi00juveuoft/juvenalpersiuswi00juveuoft_djvu.txt|author-link=Persius}}</ref>}}
[[Lactantius]], an early Christian author (ca. 240 – ca. 320), refers to this: 
{{quote|For they say that the course of human life resembles the letter Y, because every one of men, when he has reached the threshold of early youth, and has arrived at the place "where the way divides itself into two parts," is in doubt, and hesitates, and does not know to which side he should rather turn himself.<ref>{{cite book|author=Lactatius|title=The Divine Institutes|pages=Book VI Chapter III|url=http://en.wikisource.org/wiki/Ante-Nicene_Fathers/Volume_VII/Lactantius/The_Divine_Institutes/Book_VI/Chap._III|author-link=Lactantius}}</ref>}}

==Character encodings==
Upsilon and Coptic Ua characters.<ref>Unicode Code Charts: [https://www.unicode.org/charts/PDF/U0370.pdf Greek and Coptic (Range: 0370-03FF)]</ref>

* {{unichar|01B1|html=}}
* {{unichar|028A|html=}}
* {{unichar|038E|html=}}
* {{unichar|03A5|html=}}
* {{unichar|03AB|html=}}
* {{unichar|03B0|html=}}
* {{unichar|03C5|html=}}
* {{unichar|03CB|html=}}
* {{unichar|03CD|html=}}
* {{unichar|03D2|html=}}
* {{unichar|03D3|html=}}
* {{unichar|03D4|html=}}
* {{unichar|1D7F|html=}}
* {{unichar|1DB7|html=}}
* {{unichar|1F50|html=}}
* {{unichar|1F51|html=}}
* {{unichar|1F52|html=}}
* {{unichar|1F53|html=}}
* {{unichar|1F54|html=}}
* {{unichar|1F55|html=}}
* {{unichar|1F56|html=}}
* {{unichar|1F57|html=}}
* {{unichar|1F59|html=}}
* {{unichar|1F5B|html=}}
* {{unichar|1F5D|html=}}
* {{unichar|1F5F|html=}}
* {{unichar|1F7A|html=}}
* {{unichar|1F7B|html=}}
* {{unichar|1FE0|html=}}
* {{unichar|1FE1|html=}}
* {{unichar|1FE2|html=}}
* {{unichar|1FE3|html=}}
* {{unichar|1FE6|html=}}
* {{unichar|1FE7|html=}}
* {{unichar|1FE8|html=}}
* {{unichar|1FE9|html=}}
* {{unichar|1FEA|html=}}
* {{unichar|1FEB|html=}}
* {{unichar|2CA8|html=}}
* {{unichar|2CA9|html=}}
* {{unichar|1D6BC|html=}}
* {{unichar|1D6D6|html=}}
* {{unichar|1D6F6|html=}}
* {{unichar|1D710|html=}}
* {{unichar|1D730|html=}}
* {{unichar|1D74A|html=}}
* {{unichar|1D76A|html=}}
* {{unichar|1D784|html=}}
* {{unichar|1D7A4|html=}}
* {{unichar|1D7BE|html=}}

== Notes ==
{{Reflist}}

==External links==
{{Wiktionary|Υ|υ}}
{{Commons category}}
* {{cite web|last=Merrifield|first=Michael|title=Υ – Mass to Light Ratio|url=http://www.sixtysymbols.com/videos/masstolight.htm|work=Sixty Symbols|publisher=[[Brady Haran]] for the [[University of Nottingham]]|year=2009}}

[[Category:Greek letters]]
[[Category:Vowel letters]]